[Pw_forum] graphite cell optimization failed

[Eric Germaneau]

Dear all,

For people who are interested here is the result of my graphite 
calculations including vdW-DF method from the release 4.3.


GGA                                            GGA - london GGA - 
vdW-DF                           LDA                                  EXP

a = 2.46854 angs                  a =  2.46283 angs a = 2.47107  angs 
                    a = 2.44424                  a = 2.46067
c = 8.02141 angs  (1.3514)    c =  6.39949 angs (0.2705) c = 7.27887 
angs (0.60887)    c = 6.49579 (0.1742)    c = 6.705 (6.67 at 0K)

The number in parenthesize is abs(exp-calc).
 From my calculations the best option after LDA approach to include vdW 
interactionsis still GGA + London.
I thank you again for your help.

                  Eric.


On 03/24/2011 01:45 PM, Eric Germaneau wrote:
> Dear QE users,
>
> First of all I thank you all so much for your very useful replies and 
> advices.
> I did again the calculation this time using 16x16x8 k-points with cold 
> smearing  as suggested in PRB 71, 205214 (2005).
> I've also increased the precision of the atomic coordinates.
> Finally, I preformed the calculation using GGA only, GGA+london, and LDA.
> I got the following results:
>
> GGA                             GGA - 
> london                                
> LDA                                                             EXP
>
> a = 2.46854 angs       a =  2.46283 angs                          a = 
> 2.44424                                         a = 2.46067
> c = 8.02141 angs       c =  6.39949 angs                          c = 
> 6.49579                                         c = 6.705 (6.67 at 0K)
> energy = -155.032      energy =  -155.146 ev/atom           energy = 
> -155.481 ev/atom
>
> The DFT-D approach improve significatively the length of the c axis.
> I'm currently trying to do the same thing with the vdW-DF method 
> implemented in QE 4.3a but the program crash with the error:
>
> /     from ggen : error #     45126
>      too many g-vectors/
>
> Best,
>
>              Eric.
>
> On 03/23/2011 12:33 PM, Eric Germaneau wrote:
>> Dear all,
>>
>> I'm trying to optimize unit cell parameter of graphite.
>> The problem is the c axis gets too long.
>> Starting from published data my initial parameters are a=4.59203 Bohr 
>> and c=12.513 Bohr.
>> The final values are 4.664 and 15.829 respectively.
>> I need someone to explain to me what I did wrong, I've attached my 
>> input file.
>> That's a basic calculation so it's very frustrating to not make it done.
>> I thank you in advance,
>>
>>                                     Eric.
>>
>> -- 
>> /Be the change you wish to see in the world
>> / --- Mahatma Gandhi ---
>>
>> Dr. Éric Germaneau <mailto:germaneau at gucas.ac.cn>
>>
>> College of Physical Sciences
>> Graduate University of Chinese Academy of Sciences
>> Yuquan Road 19A
>> Beijing 100049
>> China
>>
>> /Please consider the environment before printing this email.
>> Considérez svp l'environnement avant d'imprimer cet email. /
>>
>>
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>
> -- 
> /Be the change you wish to see in the world
> / --- Mahatma Gandhi ---
>
> Dr. Éric Germaneau <mailto:germaneau at gucas.ac.cn>
>
> College of Physical Sciences
> Graduate University of Chinese Academy of Sciences
> Yuquan Road 19A
> Beijing 100049
> China
>
> /Please consider the environment before printing this email.
> Considérez svp l'environnement avant d'imprimer cet email. /
>
>
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-- 
/Be the change you wish to see in the world
/ --- Mahatma Gandhi ---

Dr. Éric Germaneau <mailto:germaneau at gucas.ac.cn>

College of Physical Sciences
Graduate University of Chinese Academy of Sciences
Yuquan Road 19A
Beijing 100049
China

/Please, if possible, don't send me MS Word or PowerPoint attachments
Why? See: http://www.gnu.org/philosophy/no-word-attachments.html /

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